I have used bash, zsh, ksh, and now powershell. I am by no means an expert on UNIX shells. I could get all my work done on any one of these. My main shell is Zsh with some oh-my-zsh plugins because I’m lazy. What can you do in powershell that you can’t do in any other shell? Also, does the shell you use even matter? Sorry if this is a dumb question.
Genuine question, but how is functionally more limited? You can still run any executable, munge text outputs, and… Well, isn’t that what just about any shell do?
On top of that, you can play with objects on the pipeline, which fewer shells support.
Edit: perhaps you mean in comparison to scripting tools, e.g. Python? I had read the OP to be asking more about it as a shell, I think.